Method and apparatus for forming metal containers



1965 R. R. BOLT ETAL 3,203,218

METHOD AND APPARATUS FOR FORMING METAL CONTAINERS Filed May 22, 1961 3Sheets-Sheet 1 IN VEN TOR BMW/IEO P055? 7 5 0L 7 051.55? 7' EDMUND14/0555 1965 R. R. BOLT ETAL 3,203,218

METHOD AND APPARATUS FOR FORMING METAL CONTAINERS Filed May 22, 1961 3Sheets-Sheet 2 III .7. /7

iii

062 55,9 7' EDMUND WOBBE N Aug. 31, 1965 R. BOLT ETAL 3,203,218

METHOD AND APPARATUS FOR FORMING METAL CONTAINERS Filed May 22. 1961 3Sheets-Sheet 5 IN VEN TORS.

19/066450 P036797 50L T DELBEPTEDMU/VD W055E A 7' TUBA/E75 United StatesPatent The present invention relates to the production of thin walledcup-shaped containers and has particular reference to an improved methodof and apparatus for forming a metal container having a sidewall and anend integral therewith from a thin flat blank in a single continuousrelatively short operating stroke.

Devices and processes have already been proposed and used for formingtubular containers from a flat blank in a continuous stroke,particularly containers made from aluminum or other soft homogeneousmetals. Generally, the procedure used involves drawing the blank intocup form in the usual manner after which in the same continuous stroke,the punch carries the drawn cup through an ironing die slightly smallerin diameter than the drawing die. As drawn the cup usually has bottomand side wall thicknesses essentially equal to the thickness of theblank. The ironing die thins the side wall of the drawn cup and forcesthe metal back thereby increasing the height of the container.Additional ironing steps may be added to achieve a desired body wallthickness and container height, generally limited, however, by thepractical length of the punch strokewhich can be used.

As used herein, the term drawing refers to the operation wherein aperipheral margin of a flat blank is turned upwardly and simultaneouslysmoothed by means of a drawing punch and die to form a cup having awrinkle free side Wall whose thickness is substantially equal to thethickness of the original blank. Subsequent redrawing of the cup merelyturns up more of the endmaterial into the side wall thereby elongatingthe side wall but resulting in a substantial reduction in the diameterof the cup.

Ironing refers to the operation wherein the side wall of a cup iselongated by reducing its thickness with no appreciable reduction in thediameter of the cup. It is generally accomplished by placing the cup ona closely fitting punch or mandrel and forcing the cup and mandrelthrough an ironing or reducing die whose diameter is slightly less thanthe outer diameter of the cup thereby forcing the excess metal back andproducing a longer but thinner side wall.

Heretofore, the drawing and ironing method described has not beenconsidered an economical method for the high speed production of steelcontainers having a large aspect or height to diameter ratio, e.g., thedimensions of the ordinary tin plate can. This is due in part to thegreater difiiculty of cold forming a hard, tough material such as steelresulting in a relatively small reduction per die. Since a drawingoperation is generally limited to forming a blank into a cup no longerthan half its diameter, the number of successive ironing operationsrequired to thin the side wall sufliciently to produce a satisfactorycontainer length in the same continuous operation necessitates a ratherlengthy punch stroke. Because a reciprocating action is involved whichcreates large inertia forces in the machine parts, a lengthy punchstroke imposes severe limits on the production rate which can beachieved.

However, by the novel method and means disclosed herein, a flat steelblank may be'formed using a combination drawing and ironing die into athin-walled container having a larger height to diameter ratio thancould 3,203,218 Patented Aug. 31, 1965 be obtained by single die meanspreviously used. In a more important application, the subject inventionutilizes additional ironing dies positioned in close succession with thecombination drawing and ironing die in a novel manner which causes theforming punch to exert a substantially uniform total force on the metalas it is being simultaneously formed in successive dies. This results inthe formation of steel containers having a relatively large height todiameter ratio in a single continuous stroke with an increasedefliciency and a reduced forming punch stroke as compared withprocedures heretofore used.

Accordingly, an object of the present invention is to provide animproved method of forming a thin-walled cup-shaped steel containerwhich will overcome the problems hereinbefore pointed out.

Another object is to provide such a method wherein a maximum amount ofworking of the metal is accomplished in a minimum of operating stroke.

Another object is to provide such a method wherein the force exerted bythe punch on the metal as it is being simultaneously formed insuccessive dies is maintained at a substantially uniform level.

A further object is to provide an apparatus for forming a cup-shapedsteel container having an end thickness equal to and a side wallthickness substantially less than the thickness of the original blank.

Yet a further object is to provide such an apparatus which requires ashorter forming punch stroke as compared to procedures heretofore used.

Numerous other objects and advantages of the invention will be apparentas it is better understood from the following description, which, takenin connection with the accompanying drawings, discloses a preferredembodiment thereof.

The above objects are accomplished in the present invention by providinga flat circular blank B of thin steel such as tin plate. A blank holderH positions the blank B over an annular die A and presses a peripheralmarginal portion of the blank against the die with a substantialpredetermined force. The die A has a combined drawing and ironingsurface compn'sing a rounded drawing face D merging with a uniformdiameter ironing face I which forms the minimum internal diameter of thedie.

A punch P forces the blank B through the die A to 4 form the flat blankinto a cup-shaped article. The blank is initially drawn as the marginalportion is pulled from beneaththe blank holder H and over the drawingface D. The holding force maintained by the blank holder H on themarginal edge portion of the blank B prevents wrinkling or folding ofthe blank and insures that the blank is smoothly stretched as it isbeing drawn.

As the metal leaves the drawing face D, it moves immediately past theironing face I where the side wall of the cupped portion is ironedbetween the ironing face and the punch P. Upon emerging from the die A,the end of the cup-shaped article formed thereby has a thicknesssubstantially equal to the thickness of the blank B, While the side Wallthickness is substantially less than the thickness of the blank.

The side wall is subsequently decreased in thickness in the samecontinuous stroke by forcing it through one or more ironing diespositioned below and in close succession to the drawing die A. Thediameters of the ironing faces and the spacing therebetween have valueswhich cause the cup to enter each succeeding die before completelyemerging from the preceding die and which result in a substantiallyuniform force being exerted on the metal by the punch P during theportion of the operating cycle wherein the side wall portion issimultaneously being formed by successive dies.

Referring to the drawings:

FIGURE 1 is a sectional view of an apparatus embodying features of thepresent invention;

FIGURES 2 through 5 are fragmentary views similar to FIGURE 1 showing ablank being formed to a desired container configuration;

FIGURE 6 is an enlarged fragmentary sectional view showing the profileof the combination drawing and ironing die.

As a preferred or exemplary embodiment of the instant invention FIGURE 1shows a hydraulic press generally designated 11 having a die carrier 12attached to a frame 13. An annular die A having a die aperture 14 issuitably mounted in the die carrier 12. The die aperture 14 has acombined drawing and ironing surface comprising a rounded drawing face Dadjacent the upper surface of the die which curves towards and becomestangent to a constant diameter ironing face I forming the minimumdiameter of the die aperture (FIGURE 6).

A cylindrical forming punch P reciprocatably mounted above the die A inaxial alignment with the die aperture 14 has a lower end surface 15. Theshape of the end surface 15 determines the end shape of the article tobe formed and may be flat, conical, spherical, or a combination of theseshapes. In the preferred embodiment shown in the drawings, a flat endsurface 15 is used for producing fiat ended containers.

A flat,circular blank B is inserted between the die A and an annularblank holder H disposed above the die. The blank holder H has an innerdiameter slightly greater than the diameter of the punch D and a spacedseries cular recessed portion of substantially the same diameter as thatof the blank B and a depth which is slightly less than the thickness ofthe blank, the recessed portion 1 serving to position the blank in axialalignment with the die aperture 14. As thus positioned, a marginal edgeportion 23 of the blank B is gripped between the die A and the blankholder H with a substantial predetermined force due to the action ofcompressed springs 24 disposed on the stud shanks 18 between the blankholder and stud heads The upper end of the punch P is attached to thepiston rod 26 of a hydraulic actuating cylinder 27, the cylinder beingsecured to the frame 13 of the machine and having upper and lower ports,28 and 29 respectively. The admission-of pressurized hydraulic fluidfrom a suitable source (not shown) to the cylinder 2'7 through the upper'port 28 moves the punch P downwardly bringing the lower end surface 15of the punch into contact with the blank B.

The punch P continuing to move downwardly progressively pulls themarginal edge portion 23 of the blank B from beneath the blank holder Hand forces it into contact with the drawing face D of the die A. Themarginal edge portion 23 is thus drawn across the drawing face 1D and isstretched and shaped into a tubular configuration to form a side wallportion 30 of a cupshaped article having an end 33 (FIGURE 2). The sidewall portion 30 as well as the end 33 of the drawn article havethicknesses substantially equal to the thickness of the blank B.

Concurrently with the formation of the drawn side wall portion 30 by thedrawingface D, the part of the drawn side Wall leaving the drawing faceis immediately moved past the adjacent ironing face I of the combinationdie A.

The ironing face I reduces the thickness of the side wall andcorrespondingly increases its length.

During this combination drawing and ironing operation, the force withwhich the marginal edge portion 23 of the blank B is gripped between theblank holder H and die A is maintained at a level suflicient to insurethat the blank is plastically stretched rather than being wrinkled orfolded as the marginal portion is withdrawn from beneath the blankholder but is not so great as to result in tearing or cracking of themetal. The metal is thus simultaneously subjected to three types ofloading in the combination drawing and ironing operation, i.e., acompressive loading on the marginal edge portion 23 of the blank B dueto the holding force, a tension or stretching load on the metal adjacentthe drawing face D as the metal is drawn from the fiat to the tubularform, and a compressive type loading on the metal adjacent the ironingface I as the side wall is ironed and reduced in thickness. By workingthe metal in this manner, it has been found that the amount of ironingof the drawn side wall portion 30 which can be accomplished by theironing face I is greater than could be achieved by first completelydrawing a cup and thereafter ironing the side wall of the drawn cup.

While not wishing to be bound by any particular theory, it is believedthat this result is due to a high back stress in the metal as it entersthe ironing face I. This apparently permits the greater deformation ofthe metal without creating an excessively high die pressure at theironing face which would tend to cause tearing and rupturing of themetal.

Generally, the holding force used will be determined by the particularforming operation. For example, in the combined drawing and ironing of a6 /8" x .019" thick soft steel blank into a diameter cup having an .014"side wall thickness, a holding force equivalent to approximately 10,000lbs. on the marginal edge portion of the blank is preferred.

While still engaged by the ironing face I, the cupshaped article entersan annular ironing die 34 mounted in the die holder 12 below thecombination die A (FIG- URE 3). The ironing die 34 has an ironing face35 which is smaller than and axially aligned with the ironing face I ofthe combination die A. A spacer plate 36 is disposed between thecombination die A and ironing die 34 to produce a predetermined spacingbetween the respective ironing faces I and 35 of the dies. The downwardmovement of the punch P forces the side wall portion of the cup-shapedarticle past the ironing face 35 reducing the thickness of and therebyelongating the side wall portion.

A second ironing die 37 having an ironing face 38 is similarly mountedin the die holder 12 below the ironing die 34. A spacer 39 disposedbetween the ironing dies 34 and 37 produces a predetermined spacingbetween the respective ironing faces 35 and 38 thereof. As the punch Pcontinues downwardly, it carries the cup-shaped article into the ironingface 38 while the side wall is still engaged by the ironing face 35 ofthe first ironing die 34. Depending upon the spacings between therespective ironing faces required to produce a substantially uniformpunch force, as more fully discussed hereinafter, the side wall may alsostill be engaged by the ironing face I of the combination die A when itinitially enters the ironing face 38 of the second ironing die 37(FIGURE 4). As it is moved downwardly, the side wall is then disengagedfrom the ironing face I while still engaged by the ironing faces 35 and38 of the ironing dies 34- and 37 respectively (FIGURE 5 The side wallis further ironed by the ironing face 38 to reduce its thickness andincrease its length. The drawn and ironed container 40 finally formedhas the end 33 of substantially the same thickness as that of the blankB and a side wall 43 whose thickness is substantially less than that ofthe blank. It is to be understood that, while the drawings show only twoironing dies, additional ironing dies may be used to produce any desiredside wall thickness and container height.

It has been found by extensive testing that the reduction in thethickness of the side wall of a steel cupshaped article in a series ofsuccessively aligned ironing dies is accomplished at a greatereificiency and a shorter stroke when the punch exerts a substantiallyuniform force on the metal as it is being formed as compared to the casewhere the punch exerts a fluctuating force on the metal, e.g., where thecup is forced through the dies in separate successive operating steps.Also, that a uniform punch force can be achieved by using apredetermined combination of ironing face sizes and spacings whereby themetal is simultaneously engaged and being worked by successive ironingfaces. For a particular desired container configuration, variouscombinations of these parameters may be used to accomplish the sametotal working of the metal, e.g., a large number of closely spacedironing faces with a small reduction in thickness per ironing face ascompared to a lesser number of more widely spaced ironing faces with alarge reduction in side wall thickness by each ironing face. Generally,it is preferable to have each ironing face spaced from the precedingironing face a distance no greater than 75% of the length of the sidewall which is formed by the preceding ironing face.

The continuous downward movement of the punch P carries the formedcontainer through a conventional stripper disposed below the die A. Thestripper consists of a segmented fiat annular ring 44 having a series ofsegments 45 adapted to slide radially within a recessed portion 46 inthe lower surface of the die holder 12. The segments 45 are urgedradially inwardly by springs 47 and are retained within the recessedportion 46 by an annular flat retaining ring 48 secured to the dieholder 12 by screws 49. At the extreme inwardly position of the segments45, the segmented ring 44 has a substantially cylindrical inner surface50 whose diameter is slightly less than the diameter of the punch P witha smoothly rounded upper edge 53 and a sharp lower edge 54.

As the formed container 40 is conveyed toward the stripper by the punchP, it contacts the rounded upper edge 53 of the segmented ring 44forcing the segments 45 outwardly to allow the punch and container topass through the ring. After the container has passed through the ring44, the springs 47 move the segments 45 inwardly against the punch P. Bysuitable valving means (not shown), the How of pressurized hydraulicfluid is then directed to the lower port 29, whereupon the punch P ismoved upwardly by the actuating cylinder 27. During the upward movementof the punch P, the upper edge of the formed container engages the sharplower edge 54 of the segmented ring 44 which prevents any further upwardmovement of the container thereby stripping it from the punch.

By the use of the apparatus described, which also exemplifies the methodsteps required for consummating the process of the invention, it ispossible to form in a single continuous operation a cup-shaped steelcontainer at a higher efliciency and using a shorter punch stroke thanheretofore required. The container thus formed may have a relativelyshort side wall height by employing a single combination drawing andironing operation, or the side Wall may be relatively long as comparedto the diameter of the container by using additional ironing steps.Since by the subject method the deforming force exerted by the punch onthe metal is maintained at a maximum value during the greatest portionof its stroke, resulting in the maximum working of the metal for a givenpunch stroke, containers having a relatively high length to diameterratio can be produced in the minimum space and time. Consequently, theprocess is particularly suited for production at higher rates of speedthan can be presently achieved.

While the foregoing description is particularly directed to the formingof steel containers because this metal is diflicult to form economicallyand at high speeds, it is to be understood that the general methoddescribed is also applicable and has advantages in the forming of othermetals such as aluminum and cop-per alloys. In any case, the moreuniform working of the metal during the punch stroke which is achievedby the subject method results in a shorter punch stroke for a giventotal work.

It is thought that the invention and many of its attendant advantageswill be understood from the foregoing description and it will beapparent that various changes may be made in the form, construction, andarrangement of the parts and that changes may be made in the steps ofthe method described and their order of accomplishment without departingfrom the spirit and scope of the invention or sacrificing all of itsmaterial advantages, the form hereinbefore described being merely apreferred embodiment thereof.

We claim:

1. A method of forming a cup-shaped one piece metal container having arelatively thin side wall as compared to the end thereof from a fiatblank having a thickness equal to that of said end comprising the stepsof, holding a peripheral margin of said blank with a substantialpredetermined force, maintaining said force while passing said blankthrough a die element, during said passage through said die elementdrawing said blank into a form comprising a drawn side wall portion andan end portion each having a thickness substantially equal to thethickness of said blank, and immediately thereafter and withoutinterruption as the drawing of each incremental length of said side wallportion is completed ironing each said incremental length of said drawnside wall port-ion to elongate and substantially reduce the thickness ofthe same.

2. The method set forth in claim 1 having at least one additionalironing operation wherein said side wall portion is further reduced inthickness and elongated, said ironing operations being spaced no greaterthan 75 of the length of the side wall portion formed by the precedingironing operation, the total force moving said blank during said drawingand ironing operations having a maximum and substantially uniform valueduring the portion .of said movement wherein said side wall portion isbeing simultaneously subjected to successive ironing operations.

3. The method set forth in claim 2 wherein a disksha-ped blank is formedinto a cylindrical container.

4. The method set forth in claim 3 wherein the cylindrical containerthus formed has a substantially flat end, said end being disposedperpendicularly to the longitudinal axis of said container.

5. An apparatus for forming a fiat metal blank having a substantiallyuniform thickness into a cup-shaped one piece metal container having arelatively thin side Wall as compared to the end thereof and an endthickness equal to that of said blank comprising a punch having alongitudinal axis,

actuating means for forcibly moving said punch along said longitudinalaxis,

holding means adapted to position and releasably press a peripheralmargin of said blank against a holding surface with a substantialpredetermined force,

a combination one piece die having a die opening in axial alignment withsaid longitudinal axis of said punch,

said holding surface comprising a surface of said die surrounding saiddie opening,

said die opening comprising a drawing surface extending from the innerperiphery of said holding surface and merging into an ironing surfacedisposed immediately adjacent to said holding surface, said holding,drawing and ironing surfaces forming a continuous unbroken one-pieceworking surface of said die adapted to initially draw said peripheralmargin of said blank into a drawn side wall portion and immediatelysubsequent and without interruption to iron said drawn side wall portionto substantially reduce the thickness thereof as said punch is movedthrough said die opening,

said holding means being adapted to maintain said force on the portionof said peripheral margin in contact with said holding surface as saidperipheral margin is progressively withdrawn from said holding means andforced throu-gh said die opening by the action of said punch, at leastone ironing die having an ironing surface of predetermined size disposedbelow and in axial alignment with the ironing surface of saidcombination die, said ironing surfaces of said dies having apredetermined spacing therebetween,

said punch being adapted to carry said side wall portion past saidironing surfaces of said ironing dies whereby said side wall portion isfurther ironed to elongate and reduce the thickness thereof, saidspacing between said ironing surfaces being no greater than 75% of thelength of the side wall portion *formed by the preceding ironing surfaceso that side wall portion is initially engaged by each succeedingironing surface while a substantial length of the side wall portion hasyet to pass the preceding ironing surface, said actuating means beingadapted to continuously move said punch through said dies wi-th amaximum and substantially uniform force during the portion of saidmovement wherein said side wall portion is simultaneously engaged bysuccessive ironing surfaces.

6. The apparatus set forth in claim 5 having dies with circular ironingsurfaces and a cylindrically shaped punch, said punch and dies beingadapted to form a disk-shaped blank into a cylindrically shapedcontainer.

7. The apparatus set forth in claim 6 wherein said punch has an endsurface of predetermined con-figuration corresponding to the desiredshape of the end of said container.

8. The apparatus set forth in claim 7 wherein said end surface issubstantially flat and lies in a plane perpendicular to the longitudinalaxi-s of said punch.

9. An apparatus for forming a metal blank having a substantially uniformthicknes-s into a cup-shaped one piece hollow metal article having arelatively thin side Wall as compared to the end thereof and an endthickness equal to that of said blank comprising a punch having alongitudinal axis,

means for forcibly moving said punch along said longitudinal axis,

holding means adapted to position and releasably press I a peripheralmargin of said blank against a holding surface with a substantialpredetermined force,

and unitary die means having a die opening in axial alignment with saidlongitudinal axis of said punch,

said holding surface comprising a surface of said die means surroundingsaid die opening,

said die opening comprising a drawing surface extending from the innerperiphery of said holding surface and merging into an ironing surfacedisposed immediately adjacent to said holding surface, said holding,drawing and ironing surfaces forming a continuous unbroken one-pieceworking surface of said die ineans adapted to initially draw saidperipheral margin of said blank into a drawn side wall portion andimmediately subsequent and without interruption to iron said drawn sidewall portion to substantially reduce the thickness thereof as said punchis moved through said die opening,

said holding means being adapted to maintain said force on the portionof said periphreal margin in contact with said holding surface as saidperipheral margin is progressively withdrawn from said holding means andforced through said die opening by the action of said punch.

References Cited by the Examiner UNITED STATES PATENTS 2,25 5,1 1 6 9/41Helmstaede-r 113-42 XR 2,270,186 1/42 Dud mage 113-42 XR 2,412,813 12/46Keller 113-49 2,531,663 11/50 Biginelli et a1. 113-42 2,545,570 3/51Caldwell 113-42 2,559,679 7/51 See 113-49 XR 2,615,412 10/52 Rhodes113-46 2,73 5,390 2/56 Engell 113-51 2,761,406 9/56 Schnell 113-462,821,156 1/58 Lyon 113-49 2,972,97d 2/ 61 Hillgren 1 13-51 FOREIGNPATENTS 523,111 4/31 Germany.

WILLIAM J. STEPHENSON, Primary Examiner.

NEDW-IN BERGER, MICHAEL V. BRINDISI,

Examiners.

9. AN APPARATUS FOR FORMING A METAL BLANK HAVING A SUBSTANTIALLY UNIFORMTHICKNESS INTO A CUP-SHAPED ONE PIECE HOLLOW METAL ARTICLE HAVING ARELATIVELY THIN SIDE WALL AS COMPARED TO THE END THEREOF AND AN ENDTHICKNESS EQUAL TO THAT OF SAID BLANK COMPRISING A PUNCH HAVING ALONGITUDINAL AXIS, MEANS FOR FORCIBLY MOVING SAID PUNCH ALONG SAIDLONGITUDINAL AXIS, HOLDING MEANS ADAPTED TO POSITION AND RELEASABLYPRESS A PERIPHERAL MARGIN OF SAID BLANK AGAINST A HOLDING SURFACE WITH ASUBSTANTIAL PREDETERMINED FORCE, AND UNITARY DIE MEANS HAVING A DIEOPENING IN AXIAL ALIGNMENT WITH SAID LONGITUDINAL AXIS OF SAID PUNCHSAID HOLDING SURFACE COMPRISING A SURFACE OF SAID DIE MEANS SURROUNDINGSAID DIE OPENING,